It works by using a picture that contains both the object to be measured as well as an object of known length.  Once the picture is selected, two sets of markers are placed on the picture.  The red markers are set at the endpoints of the object of known length and the black markers are set at the endpoints of the object of unknown length.  Here we set the red markers to set the height of the “O” in college. The total height of the gate is estimated by pacing one black marker at the base of the pillar and the other above the “G” in College. Next, the length between the red markers are entered in inches.  The app then calculates the distance between the black markers, thus showing the length of the object.

Click on the phone to see a video of the app in action.